1,2-dichlorobenzene

Biotransformation and kinetics

Administrative data

Endpoint:

biotransformation and kinetics

Type of information:

other: BUA report

Adequacy of study:

other information

Reliability:

other: BUA report

Rationale for reliability incl. deficiencies:

other: BUA report

Data source

Reference

Reference 1

Reference Type:

other: BUA report

Title:

Unnamed

Year:

1990

Reference 2

Reference Type:

publication

Title:

An ecological approach to the problem of biodegradation of phenole wastes

Author:

Cobb HD, Atherton R, Olive W

Year:

1974

Bibliographic source:

Rep No AFOSR-TR-75-0070; AD/A-004517, National Technical Information Service (NTIS), Springfield, VA, 1-18

Reference 3

Reference Type:

publication

Title:

Mikrobieller Abbau von chlorierten Aromaten: VI. Bildung von Dichlorphenolen und Dichlorbrenzkatechinen aus Dichlorbenzolen in mikromolarer Lösung durch Pseudomonas sp. [in German]

Author:

Ballschmiter K, Scholz C

Year:

1980

Bibliographic source:

Chemosphere, 9: 457-467

Reference 4

Reference Type:

publication

Title:

Primärschritte der Umwandlung von Chlorbenzol-Derivaten durch Pseudomonas putida [in German]

Author:

Ballschmiter K, Scholz C

Year:

1981

Bibliographic source:

Angew Chem, 93: 1026-1027

Reference 5

Reference Type:

publication

Title:

Bildung von Chlorphenolen durch mikrobielle Umwandlung von Chlorbenzolen [in German]

Author:

Ballschmiter K, Unglert C, Heizmann P

Year:

1977

Bibliographic source:

Angew Chem, 89: 680-681

Reference 6

Reference Type:

publication

Title:

Biologischer Abbau mehrfach halogenierter mono- und polyzyklischer Aromaten [in German]

Author:

Springer W, Rast HG

Year:

1988

Bibliographic source:

GWF. Gas-Wasserfach: Wasser Abwasser 129: 70-75

Reference 7

Reference Type:

publication

Title:

Degradation of 1,4-dichlorobenzene by a Pseudomonas sp.

Author:

Spain JC, Nishino SF

Year:

1987

Bibliographic source:

Appl Environ Microbiol, 53: 1010-1019

Reference 8

Reference Type:

publication

Title:

Degradation of 1,2-dichlorobenzene by a Pseudomonas sp

Author:

Haigler BE, Nishino SF, Spain JC

Year:

1988

Bibliographic source:

Appl Environ Microbiol, 54: 294-301

Reference 9

Reference Type:

publication

Title:

Degradation of chlorinated and non-chlorinated aromatic solvents in soil suspensions by pure bacterial cultures

Author:

Oldenhuis R, Kuijk L, Lammers A, Janssen DB, Witholt B

Year:

1989

Bibliographic source:

Appl Microbiol Biotechnol, 30: 211-217

Materials and methods

Principles of method if other than guideline:

BUA report

GLP compliance:

not specified

Test material

Test material information

Constituent 1

Reference substance name:

1,2-dichlorobenzene

EC Number:

202-425-9

EC Name:

1,2-dichlorobenzene

Cas Number:

95-50-1

Molecular formula:

C6H4Cl2

IUPAC Name:

1,2-dichlorobenzene

Results and discussion

Any other information on results incl. tables

BUA report:

Several studies on the biotransformation of 1,2-dichlorobenzene were summarized in the assessment of the BUA report 53 (1990). Some of these studies were reliable studies with restrictions, or reliability was not assignable because references were only cited as secondary literature.

For the investigation of the biodegradation of o-dichlorobenzen by Pseudomonas, 19 strains of the Pseudomonas group, including P. aeruginosa, P. fluorescens and P. putida, were isolated, which proved able to utilize the three cresol isomers as the sole source of carbon and energy. Exposure of these bacteria to o-dichlorobenzene vapours (no information is provided about concentration) led to growth in all 19 strains, even in the absence of any other source of carbon.

Biotransformation of o-dichlorobenzene to 2,3 -, 3,4- and 2,6 -dichlorophenol was demonstrated in selected mixed cultures of soil bacteria in the presence of benzene as the sole carbon source and pure cultures of Pseudomonas putida. The formation of the first two metabolites is evidence that 5,6 -dichlorocyclohexan-3,5 -dien-1,2 -diol is formed as an intermediate whereas the formation of 2,6 -dichlorophenol points to rearrangement of an alpha-dichloroepoxide.

In further studies involving pure Pseudomonas cultures as well as isolated mixed cultures, GC-ECD techniques revealed the metabolites to be 3,4 - and 4,5- dichlorocatechol, and, after 100 hours' incubation, 2,4 -dichlorophenol and 3,5 -dichlorocatechol. A metabolite pattern that was qualitatively similar was obtained at a much faster rate when o-dichlorobenzene was incubated with phenobarbitone-induced rat liver microsomes.

From the River Rhine and various industrial wastewater-treatment plants, bacteria of the genera Pseudomonas, Acinetobacter and Moraxella, which can utilize o-dichlorobenzene as the sole source of carbon, were isolated. Incubation of o-dichlorobenzen with a Pseudomonas or Acinetobacter strain, either of which was able to utilize a broad spectrum of substrates, led to specific chloride-formation rates of 1770 to 2400 µmol/(L*h*g dry weight). The molar ratio of substrate to generated chloride was 1:2, i.e., o-dichlorobenzene was quantitatively dehalogenated under aerobic conditions.

In further studies, Pseudomonas species (strain JS 6) was isolated from activated sludge that was able to utilize p-dichlorobenzene as the sole source or carbon and energy and that was also able to degrade o-dichlorobenzene. Another strain (JS 100) was also isolated from activated sludge after selective enrichment. It was also able to utilize o-dichlorobenzene as the sole source of carbon and energy. Furthermore, this strain of bacteria, which required at least 5.5 hours to double in number in the presence of gaseous o-dichlorobenzene, converted o-dichlorobenzene to carbon dioxide and chloride ions. Cells precultivated with o-dichlorobenzene consumed 151 nmol of oxygen per minute per milligramme of protein with o-dichlorobenzene as substrate and released 2.31 mole of chloride per mole of substrate (Some of the chloride apparently stemmed from the substrate of the preculture.) Use of 14C-labelled o-dichlorobenzene showed that 40.2% of the radioactively labelled carbon was in the form of CO2. The remainder, minus losses due to volatility, was present in the biomass (13.7%) and, partially metabolized, in the culture filtrate (36.7%). No CO2 (< 0.01%) or water-soluble metabolites could be detected in control samples sterilized with formaldehyde.

An account of trials is given for degrading o-dichlorobenzene by a Pseudomonas strain (GJ 60) which was comparable in terms of substrate specificity to the JS 100 strain mentioned above. This strain was isolated and cultivated from Rhine sediment with o-dichlorobenzene serving as the sole source of carbon. A solution of 50 mg/l of o-dichlorobenzene in a suspension of garden soil which had been inoculated with it (5 mg (dry weight) per litre) was degraded rapidly and completely within 50 hours at 30 °C. In order to prevent adsorption as a means of elimination, the soil had been stored for two months in a 73.5 mg/l aqueous solution of o-dichlorobenzene.

Applicant's summary and conclusion

Executive summary:

Several studies on the biotransformation of 1,2-dichlorobenzene were summarized in the assessment of the BUA report 53 (1990). Some of these studies were reliable studies with restrictions, or reliability was not assignable because references were only cited as secondary literature.

For the investigation of the biodegradation of o-dichlorobenzen by Pseudomonas, 19 strains of the Pseudomonas group, including P. aeruginosa, P. fluorescens and P. putida, were isolated, which proved able to utilize the three cresol isomers as the sole source of carbon and energy. Exposure of these bacteria to o-dichlorobenzene vapours (no information is provided about concentration) led to growth in all 19 strains, even in the absence of any other source of carbon.

Biotransformation of o-dichlorobenzene to 2,3 -, 3,4- and 2,6 -dichlorophenol was demonstrated in selected mixed cultures of soil bacteria in the presence of benzene as the sole carbon source and pure cultures of Pseudomonas putida. The formation of the first two metabolites is evidence that 5,6 -dichlorocyclohexan-3,5 -dien-1,2 -diol is formed as an intermediate whereas the formation of 2,6 -dichlorophenol points to rearrangement of an alpha-dichloroepoxide.

In further studies involving pure Pseudomonas cultures as well as isolated mixed cultures, GC-ECD techniques revealed the metabolites to be 3,4 - and 4,5- dichlorocatechol, and, after 100 hours' incubation, 2,4 -dichlorophenol and 3,5 -dichlorocatechol. A metabolite pattern that was qualitatively similar was obtained at a much faster rate when o-dichlorobenzene was incubated with phenobarbitone-induced rat liver microsomes.

From the River Rhine and various industrial wastewater-treatment plants, bacteria of the genera Pseudomonas, Acinetobacter and Moraxella, which can utilize o-dichlorobenzene as the sole source of carbon, were isolated. Incubation of o-dichlorobenzen with a Pseudomonas or Acinetobacter strain, either of which was able to utilize a broad spectrum of substrates, led to specific chloride-formation rates of 1770 to 2400 µmol/(L*h*g dry weight). The molar ratio of substrate to generated chloride was 1:2, i.e., o-dichlorobenzene was quantitatively dehalogenated under aerobic conditions.

In further studies, Pseudomonas species (strain JS 6) was isolated from activated sludge that was able to utilize p-dichlorobenzene as the sole source or carbon and energy and that was also able to degrade o-dichlorobenzene. Another strain (JS 100) was also isolated from activated sludge after selective enrichment. It was also able to utilize o-dichlorobenzene as the sole source of carbon and energy. Furthermore, this strain of bacteria, which required at least 5.5 hours to double in number in the presence of gaseous o-dichlorobenzene, converted o-dichlorobenzene to carbon dioxide and chloride ions. Cells precultivated with o-dichlorobenzene consumed 151 nmol of oxygen per minute per milligramme of protein with o-dichlorobenzene as substrate and released 2.31 mole of chloride per mole of substrate (Some of the chloride apparently stemmed from the substrate of the preculture.) Use of 14C-labelled o-dichlorobenzene showed that 40.2% of the radioactively labelled carbon was in the form of CO2. The remainder, minus losses due to volatility, was present in the biomass (13.7%) and, partially metabolized, in the culture filtrate (36.7%). No CO2 (< 0.01%) or water-soluble metabolites could be detected in control samples sterilized with formaldehyde.

An account of trials is given for degrading o-dichlorobenzene by a Pseudomonas strain (GJ 60) which was comparable in terms of substrate specificity to the JS 100 strain mentioned above. This strain was isolated and cultivated from Rhine sediment with o-dichlorobenzene serving as the sole source of carbon. A solution of 50 mg/l of o-dichlorobenzene in a suspension of garden soil which had been inoculated with it (5 mg (dry weight) per litre) was degraded rapidly and completely within 50 hours at 30 °C. In order to prevent adsorption as a means of elimination, the soil had been stored for two months in a 73.5 mg/l aqueous solution of o-dichlorobenzene.